I also should mention two important things about the Wistar Institute at that time. One was – and they're important because I interacted with these people during my stay there – there was one laboratory run by a man, a well known man at that time called Edmund Farris. He was well known because he wrote a famous book called The Biology of the Laboratory Mouse, I think was the title, and it was kind of the bible of those who did research using mice. In addition to which, Edmund Farris ran what I believe is correct to say, the first artificial, that is human, Artificial Insemination Institute in the United States, and that was what housed the laboratories on the top floor of the Wistar Institute. And I did interact with the folks there and became fascinated with what was happening, because Edmund Farris had his major... his success was largely due to the availability of the Wistar rats, in particular, virgin female rats. Because at that time there was a test to determine pregnancy in women, unlike the tests that are done today, which then of course was rather crude. It involved taking a morning urine specimen, inoculating it into a part of the anatomy of a virgin female rat, and then two or three days later, opening the rat and looking at its ovaries. If the vessels, the blood vessels surrounding the ovaries were swollen and red, it meant that the... that the... that estrogen and other hormones produced by women at the time of conception, were now being made in greater quantities and easily identified by this method. It was called 'the Aschheim-Zondek test', a test that's no longer done. With that capability, Edmund Farris was able to determine, of course, the ovulation time of a woman who wanted to become pregnant, and was very successful in doing artificial insemination. The sperm was contributed by graduate students and medical students at the University of Pennsylvania. This was a very successful enterprise. I remember distinctly women coming up the stairs, this great set of wrought iron stairs that's... that's iconic for the Wistar Institute, carrying a young baby in order to show it to Dr Farris and express their pleasure with what he had succeeded in helping them do.